Some items of large mining machinery, such as excavators and shovels, are fitted with crawler tracks for locomotion. In vehicles driven by endless crawler tracks such as surface mining shovels, excavators, bulldozers and tanks the crawler tracks include a series of links which are linked together by pins to form an endless articulated track, each track being mounted on support rollers with sprockets at either end. These tracks allow the machine to move along a ground surface.
The individual links of the crawler tracks are known as “shoes”. The track shoes must support a heavy weight, and are subject to high pressures. Further, the tracks are often required to operate in harsh conditions, such as stony or rock-strewn ground and low temperatures.
Presently, track shoes for heavy vehicles such as the Bucyrus 495 Mining Shovel are formed from cast steel which may be induction hardened where needed. The OEM manufacturers expected lifetime for such a track shoe is about 28,000 service hours. However, the present inventors have found that their actual average lifetime is about only 10,000 service hours. They have also found that the failure mode on such a part is more structural than wear related. Each shoe, which is 79 inches wide and weighs 3400 lbs., cost approximately $20,000. For the Bucyrus 495 Mining Shovel there are 47 of such shoes per side, for a total of 94 shoes. This adds up to a total cost of $1.88 million for each machine. The replacement costs for the track shoes on the 5 shovels operating at Mount-Wright mine is about $5 million per year, or about $200 per shovel operating hour.
Thus, there is a need in the art for a track shoe with increased service life.